A hospital which specialises in surgery for obese patients is preparing to operate on a man reported to be the fattest in the world.

Paul Mason, who weighs 70 stone, is expected to be taken in a specially adapted ambulance to St Richard's Hospital in Chichester for treatment over the next few weeks.

The hospital is home to the largest NHS centre for weight loss surgery in the South of England and currently treats more than 200 patients a year.

The unit has a team of specialist surgeons with a worldwide reputation for work on seriously obese patients.

The unit regularly features on the Discovery Channel's health documentary programme about the treatment of obesity.

Mr Mason, 48, who is classed as super-obese will have to travel 150 miles from his home in Ipswich for treatment that could potentially save his life.

The NHS had considered using a Chinook helicopter to airlift Mr Mason to hospital but have opted for an ambulance instead.

According to reports Mr Mason's weight dipped to 45 stone in 2007 but he has since put on another 25 stone.

The former engineer, who is 5ft 6in, once admitted admitted an addiction to eating and has had an intake of up to 20,000 calories a day.

He has spent much of the past eight years bedridden.

His operation is expected to cost the NHS around £20,000.

A spokeswoman for Western Sussex Hospitals NHS Trust, which runs St Richard's, refused to comment on Mr Mason or discuss the treatments and services the hospital provides.

Suffolk Primary Care Trust is overseeing Mr Mason's care.

Medical director Andrew Hassan said: “ We have a duty to protect the confidentiality of all of our patients. As such, we cannot discuss individual cases.

“The patient does not wish to make any further comment and requests he is left alone.

“We always put the needs of our patients first. As such, we have a responsibility to provide the right care for all of our patients while ensuring their safety and dignity.”